• Journal of radiological science and technology
• /
• v.33 no.3
• /
• pp.261-268
• /
• 2010

This study is compared that the dose distribution by experimentation and radiation therapy planning (RTP) when the air cavity region was treated high energy photon. The dose measurements were performed with a 6 MV photon beam of linear accelerator. The polystyrene and self made acyl phantom were similar to tissue density of the human body. A parallel plate chamber was connected to an electrometer. The measurement setup was SCD (Source Chamber Distance) 100 cm and the distance of surface from air cavity was 3 cm. Absorbed dose of interface were measured by area and height. The percent depth dose were measured presence and absence of air cavity, depth according to a ratio of field size and air cavity size. The dose distribution on planning was expressed to do the inhomogeneity correction. As the area of air cavity was increased, the absorbed dose were gradually reduced. It was slightly increased, when the height of air cavity was changed from 0 cm to 0.5 cm. After the point, dose was decreased. In case of presence of air cavity, dose after distal air cavity interface was more great than absence of air cavity. The rebuild up by field size and area of air cavity occurred for field size, $4{\times}4\;cm^2$, $5{\times}5\;cm^2$ and $6{\times}6\;cm^2$, with fixed on area of air cavity, $5{\times}5\;cm^2$. But it didn't occur at $10{\times}10\;cm^2$ field size. On the contrary, the field size was fixed on $5{\times}5\;cm^2$, rebuild up occurred in area of air cavity, $4{\times}4\;cm^2$, $5{\times}5\;cm^2$. but, it did not occur for air cavity, $2{\times}2\;cm^2$, $3{\times}3\;cm^2$. All of the radiation therapy planning were not occurred rebuild up. It was required to pay attention to treat tumor in air cavity because the dose distribution of planning was different from the dose distribution of patient.

• Journal of Radiation Protection and Research
• /
• v.23 no.4
• /
• pp.259-266
• /
• 1998

There are three different types of gynecological applicator sets available in microSelectron-high dose-rate(HDR) System by Nucletron; standard applicator set(SAS), standard shielded applicator set(SSAS), and Fletcher-Williamson applicator set(FWAS). Shielding effect of a SAS without shielding material was compared with that of a SSAS with shielding material made of stainless steel(density ${\varrho}=8,000kg/m^3$) at the top and bottom of each ovoid, and of a FWAS with shielding material made of tungsten alloy(density ${\varrho}=14,000kg/m^3$ at the top and bottom of each ovoid. The shielding effects to the rectum and bladder of these two shielded applicator sets were to be measured at reference points with an ion chamber and specially designed supporting system for applicator ovoids inside of the computerized 3-dimensional water phantom. To determine the middle point of two ovoids the measurement was performed with the reference tip of ion chamber placed at the same level and at the middle point from the two ovoids, while scanning the dose with the ion chamber on each side of ovoids. The doses to the reference points of rectum were measured at 20(Rl), 25(R2), 30(R3), 40(R4), 50(R5), and 60(R6) mm located posteriorly on the vertical line drawn from M5(the middle dwell position of ovoid), and the doses to the bladder were measured at 20(Bl), 30(B2), 40(B3), 50(B4), and 60(B5) mm located anteriorly on the vertical line drawn from M5. The same technique was employed to measure the doses on each reference point of both SSAS and FWAS. The differences of measured rectal doses at 25 mm(R2) and 30 mm(R3) between SAS and SSAS were 8.0 % and 6.0 %: 25.0% and 23.0 % between SAS and FWAS. The differences of measured bladder doses at 20 mm(Bl) and 30 mm(B2) between SAS and SSAS were 8.0 % and 3.0 %: 23.0 % and 17.0 % between SAS and FWAS. The maximum shielding effects to the rectum and bladder of SSAS were 8.0 % and 8.0 %, whereas those of FWAS were 26.0 % and 23.0 %, respectively. These results led to the conclusion that FWAS has much better shielding effect than SSAS does, and when SSAS and FWAS were used for gynecological intracavitary brachytherapy in microSelectron-HDR system, the dose to the rectum and bladder was significantly reduced to optimize the treatment outcome and to lower the complication rates in the rectum and bladder.

• Journal of Radiation Protection and Research
• /
• v.23 no.3
• /
• pp.139-147
• /
• 1998

Purpose: Tissue inhomogeneity such as lung affects tumor dose as well as transmission dose in new concept of on-line dosimetry which estimates tumor dose from transmission dose using the new algorithm. This study was carried out to confirm accuracy of correction by tissue density in tumor dose estimation utilizing transmission dose. Methods: Cork phantom (CP, density $0.202\;gm/cm^3$) having similar density with lung parenchyme and polystyrene phantom (PP, density $1.040\;gm/cm^3$) having similar density with soft tissue were used. Dose measurement was carried out under condition simulating human chest. On simulating AP-PA irradiation, PPs with 3 cm thickness were placed above and below CP, which had thickness of 5, 10, and 20 cm. On simulating lateral irradiation, 6 cm thickness of PP was placed between two 10 cm thickness CPs additional 3 cm thick PP was placed to both lateral sides. 4, 6, and 10 MV x-ray were used. Field size was in the range of $3{\times}3$ cm through $20{\times}20$ cm, and phantom-chamber distance (PCD) was 10 to 50 cm. Above result was compared with another sets of data with equivalent thickness of PP which was corrected by density. Result: When transmission dose of PP was compared with equivalent thickness of CP which was corrected with density, the average error was 0.18 (${\pm}0.27$) % for 4 MV, 0.10 (${\pm}0.43$) % for 6 MV, and 0.33 (${\pm}0.30$) % for 10 MV with CP having thickness of 5 cm. When CP was 10 cm thick, the error was 0.23 (${\pm}0.73$) %, 0.05 (${\pm}0.57$) %, and 0.04 (${\pm}0.40$) %, while for 20 cm, error was 0.55 (${\pm}0.36$) %, 0.34 (${\pm}0.27$) %, and 0.34 (${\pm}0.18$) % for corresponding energy. With lateral irradiation model, difference was 1.15 (${\pm}1.86$) %, 0.90 (${\pm}1.43$) %, and 0.86 (${\pm}1.01$) % for corresponding energy. Relatively large difference was found in case of PCD having value of 10 cm. Omitting PCD with 10 cm, the difference was reduced to 0.47 (${\pm}$1.17) %, 0.42 (${\pm}$0.96) %, and 0.55 (${\pm}$0.77) % for corresponding energy. Conclusion When tissue inhomogeneity such as lung is in tract of x-ray beam, tumor dose could be calculated from transmission dose after correction utilizing tissue density.

• Journal of Radiation Protection and Research
• /
• v.26 no.2
• /
• pp.73-78
• /
• 2001

In order to find the exposure conversion coefficients for 3"X3" NaI spectrum, we measured the exposure rates with the pressurized ion chamber at 29 different areas in the range of $4{\sim}23{\mu}R\;h^{-1}$, and also measured the gamma spectra with 3"X3" and 4"X4" NaI detectors, simultaneously. The exposure conversion coefficient of the total energy method was determined using the linear relation between the measured exposure rate and the gamma spectrum energy. In order to find the exposure conversion coefficients of the energy band method, we applied the exposure conversion coefficients recommended by NCRP to the 4"X4" NaI spectra, and calculated the exposure rates due to $^{40}K,\;^{238}U$, and $^{232}Th$ series respectively. Using the linearly proportional relation between the obtained $^{232}Th$ series exposure rate and peak area of 2614 keV that represents the $^{232}Th$ series, we obtained the exposure conversion coefficients for $^{232}Th$ series. We also determined the conversion coefficients for $^{238}U$ series and $^{40}K$ using a similar method.

• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2003.09a
• /
• pp.36-36
• /
• 2003

목적 : 고감도 형광판과 필름을 이용하여 실시간으로 선량을 측정하여 IMRT 선량분포를 검증하는데 사용하는 가능성을 알아보고자 하였다. 대상 및 방법 : 본 연구에서 개발한 물팬텀은 지름 25cm 아크릴 원통과 원통의 중앙부분에 삽입되는 고감도 형광판으로 구성되어 있다. 이를 사용하여 dose linearity correction factor를 구하기 위해 dmax 지점에서 6MV x-ray를 고감도형광판에 조사하여 blurring correction factor를 구하였다. CCD를 이용하여 고감도 형광판에서 나오는 영상을 수집하였다. 고감도 형광판에서 수집한 영상의 x축 profile은 RTP에서 얻은 profile과 비교하였고, 이온전리함으로 scanning한 데이터를 이용하여 고감도 형광판과 물에서 빛에 의한 산란선 때문에 발생하는 blurring effect를 교정하였다. 여기서 계산된 blurring effect factor를 고감도 형광판에서 수집된 영상에 적용하였다. 결과 : CCD 카메라는 형광판의 전 영역을 감지할 수 있고, 조사시간은 형광판의 중첩된 영상의 선량에 비례하였다. 물팬텀에서 형광판의 blurring effect 는 가우시안 분포로 표현할 수 있었다. 또한 Deconvolution kernel은 원통 팬텀에서 지름 $\pm$5cm 이내의 범위에 위치하였고, 따라서 형광판 영상으로부터의 실제 선량분 포를 뽑아낼 수 있었다. RTP 에서 계산된 선량분포와 blurring correction factor로 교정한 후 중첩시켜 얻은 고감도 형광판 영상의 선량분포는 일치하였다. 결론 : 정기적인 IMRT 선량 검증에 대한 실시간 선량측정 방법이 개발되었다. 고감도 형광판 영상과 CCD 카메라를 사용한 물팬텀으로, IMRT 치료계획에 대한 선량분포를 검증할 수 있는 가능성을 보였다.비의 회전에 의한 오차 보정, 필름의 광학적 밀도에 관한 보정 등 여러 가지 계통적 오차들에 대한 보정들이 선량분포 확인과정의 이해와 그 기준마련에 도움이 되겠지만 우리가 다룬 원점 불일치에 비해서 상대적으로 무시할 수 있었다. 마지막으로 선량분포 확인의 최종목표인 3 차원 선량분포 확인의 실제 적용을 위한 연구가 최적화 알고리듬을 이용하여 실험 중에 있다.\times$5cm, 10$\times$10cm, 15$\times$l5cm, 20$\times$20cm인 경우, 측정하여 얻은 PSF가 0.8%, 0.2%, 0.4%, 0.2%로 약간 높지만, 두 값은 매우 유사한 것으로 나타났다. 그리고, 기존의 BSF를 이용해 구한 TAR과 BJR 25에서 권고하는 PSF를 이용해 구한 TAR을 비교한 결과 field size 에 따라 약 1%-1.5% 정도로 BSF를 이용하여 구한 TAR보다 PSF를 이용하여 구한 TAR이 1.3% 정도 높게 나타났지만, 이것은 두 값의 절대적인 차이일 뿐, 실제로는 PSF를 이용하여 구한 TAR이 측정해서 구한 TAR과는 매우 유사한 값을 보여주고 있다. 결론 : 기존의 BSF를 이용해 구한 TAR과 PSF를 이용해 구한 TAR을 비교하였을 때, 약 1.3% 정도 높게 내고 있지만, 기존의 TAR보다는 PSF를 이용해 구한 TAR이 BJR 25와 잘 일치하고 있으므로 Co-60 원격치료용 방사선 조사장치를 사용할 경우 BSF보다는 PSF를 사용하는 것이 타당한 것으로 사료된다.tokines의 변화는 비록 통계학적인 차이는 없지만 비타민 C를 사용한 환자의 cytokines이 모두 사용하지 않은 환자에 비해 감소하였음을 보였다. 비타민 C는 부작용이 거의 없는 안전한 약으로서 말기 암 환자에서 비타민 C사용은 임상 증상을 호전시키는 데 도움

• Progress in Medical Physics
• /
• v.21 no.1
• /
• pp.60-69
• /
• 2010

For treatment of Total Skin Electron beam Therapy (TSET), measurement of dose at various conditions is need on the contrary to usual radiotherapy. When treating TSET with modified Stanford technique based on linear accelerator, the energy of treatment electron beam, the spatial dose distribution and the actual doses deposited on the surface of the patient were measured by using EBT2. The measured energy of the electron beam was agreed with the value that measured by ionization chamber, and the spatial dose distribution at the patient position and the doses at several point on the patient's skin could be easily measured by EBT2 film. The dose on the patient that was measured by EBT2 film showed good agreement with the data measured simultaneously by TLD. With the results of this study, it was proven that the EBT2 film can be one of the useful dosimeter for TSET.

• The Journal of the Petrological Society of Korea
• /
• v.10 no.3
• /
• pp.202-211
• /
• 2001

Luminescence is a physical phenomenon exhibited by many non-conducting, crystalline materials, such as quartz and feldspar. Within the crystals, energy absorbed from ionising radiation frees electrons to move through the crystal lattice and some are trapped at defects in the lattice. Observable luminescence is produced by electrons, released from traps by stimulation by absorption of light, which recombine with lattice defects which act as luminescence centers - optically stimulated luminescence (OSL). In a similar way to thermoluminescence(TL) dating, controlled measurement of the OSL signal can provide a means of determining the time since the last exposure of a layer of sediment to sunlight, the age of the sediment. However, whereas in the thermoluminescence dating of sediment only part of the latent thermoluminescence signal is bleached by sunlight as the sediment is deposited and allowance must be made during the laboratory measurements for the light insensitive component, optically induced luminescence dating has the advantage of working only with light sensitive traps in the crystal. Determination of the time since deposition of Quaternary sediment samples from the OSL of quartz grains using blue light was performed. A series of experiments and recent developments relating OSL dating are described, beginning by identifying the features which make OSL signals suitable for the development of dating method. Additionally, there are suggestions as to future research for obtaining reliable ages and a comment on current best practice on procedures, with the dating results of Quaternary sediment.

• Progress in Medical Physics
• /
• v.18 no.4
• /
• pp.194-201
• /
• 2007

Although Gamma Knife irradiates much more radiation in a single session than conventional radiotherapy, there were only a few studies to measure absolute dose of a Gamma Knife. Especially, there is no report of application of International Atomic Energy Agency (IAEA) TRS-398 which requires to use a water phantom in radiation measurement to Gamma Knife. In this article, the authors reported results of the experiments to measure the absorbed dose to water of a Gamma Knife Model C using the IAEA TRS-398 protocol. The absorbed dose to water of a Gamma Knife model C was measured using a water phantom under conditions as close as possible to the IAEA TRS-398 protocol. The obtained results were compared with values measured using the plastic phantom provided by the Gamma Knife manufacturer. Two Capintec PR-05P mini-chambers and a PTW UNIDOS electrometer were used in measurements. The absorbed dose to water of a Gamma Knife model C inside the water phantom was 1.38% larger than that of the plastic phantom. The current protocol provided by the manufacturer has an intrinsic error stems from the fact that a plastic phantom is used instead of a water phantom. In conclusion, it is not possible to fully apply IAEA TRS-398 to measurement of absorbed dose of a Gamma Knife. Instead, it can be a practical choice to build a new protocol for Gamma Knife or to provide a conversion factor from a water phantom to the plastic phantom. The conversion factor can be obtained in one or two standard laboratories.

• Progress in Medical Physics
• /
• v.26 no.3
• /
• pp.168-177
• /
• 2015

For evaluating the treatment planning accurately, the quality assurance for treatment planning is recommended when patients were treated with IMRT which is complex and delicate. To realize this purpose, treatment plan quality assurance software can be used to verify the delivered dose accurately before and after of treatment. The purpose of this study is to evaluate the accuracy of treatment plan quality assurance software for each IMRT plan according to MLC DLG (dosimetric leaf gap). Novalis Tx with a built-in HD120 MLC was used in this study to acquire the MLC dynalog file be imported in MobiusFx. To establish IMRT plan, Eclipse RTP system was used and target and organ structures (multi-target, mock prostate, mock head/neck, C-shape case) were contoured in I'mRT phantom. To verify the difference of dose distribution according to DLG, MLC dynalog files were imported to MobiusFx software and changed the DLG (0.5, 0.7, 1.0, 1.3, 1.6 mm) values in MobiusFx. For evaluation dose, dose distribution was evaluated by using 3D gamma index for the gamma criteria 3% and distance to agreement 3 mm, and the point dose was acquired by using the CC13 ionization chamber in isocenter of I'mRT phantom. In the result for point dose, the mock head/neck and multi-target had difference about 4% and 3% in DLG 0.5 and 0.7 mm respectively, and the other DLGs had difference less than 3%. The gamma index passing-rate of mock head/neck were below 81% for PTV and cord, and multi-target were below 30% for center and superior target in DLGs 0.5, 0.7 mm, however, inferior target of multi-target case and parotid of mock head/neck case had 100.0% passing rate in all DLGs. The point dose of mock prostate showed difference below 3.0% in all DLGs, however, the passing rate of PTV were below 95% in 0.5, 0.7 mm DLGs, and the other DLGs were above 98%. The rectum and bladder had 100.0% passing rate in all DLGs. As the difference of point dose in C-shape were 3~9% except for 1.3 mm DLG, the passing rate of PTV in 1.0 1.3 mm were 96.7, 93.0% respectively. However, passing rate of the other DLGs were below 86% and core was 100.0% passing rate in all DLGs. In this study, we verified that the accuracy of treatment planning QA system can be affected by DLG values. For precise quality assurance for treatment technique using the MLC motion like IMRT and VMAT, we should use appropriate DLG value in linear accelerator and RTP system.

• The Journal of Korean Society for Radiation Therapy
• /
• v.22 no.1
• /
• pp.53-60
• /
• 2010

Purpose: We try to calculate EDW-factor easily with the formula applies essential data of EDW-factor and evaluate the validity through a measurement. Materials and Methods: We used the given value of GSTT (Golden Segmented Treatment Table) for the calculation of the EDW-factor. As to the experimental device, 0.6 cc farmer-type ion-chamber, an electrometer and water- phantom were used. A measurement was made at the maximum dose depth of the photon beam energy 6 MV and 15 MV under the condition that SSD (Source to Surface Distance) was 100 cm. The angle of the EDW (Enhanced Dynamic Wedge) which we use in an experiment was 60 degree, 30 degree, 20 degree in the Y1-OUT direction. We used Eclipse planning system (Varian, USA) as RTP system and the EDW-factor was calculated about all fields and EDW direction. In order to show the EDW-factor feature, a measurement was made at the selected field that verify the influence of the dependability about X, Y jaw and off-axis field. Results: When we change the Y1 field, it influence on the EDW-Factor and measured value. But the error between measured values and calculated values was less than 1%. The experimental result indicated the tendency that the error of the result of calculation and measured value becomes smaller as the EDW angle become smaller whether the calculation point (measurement point) and iso-center are same or not. The influence of the field size and energy did not show up. We simulated with the same condition using the RTP system. And we found that it makes no difference between the MU which is calculated manually by applying the EDW-Factor obtained from the commercial program and the value which is calculated by using RTP system. Conclusion: We excluded fitting value from well-known EDW-Factor formula and calculated EDW-factor with the formula applies essential data of EDW-factor only. As a result, there are no significant difference between the measured value and calculated value and it showed errors less than 1%. Also, we implemented the commercial program to calculate EDW-Factor conveniently without measure a factor on each field.